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A Level Geography > Coasts > Flashcards

Coasts Flashcards

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1
Q

What is a high energy environment?

A

exposed coasts, facing prevailing winds with long wave fetches resulting in powerful waves.
where the rate of erosion exceeds the rate of deposition
They create rocky coasts

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2
Q

What are some landforms that are created in high energy environments?

A

Headlands
Cliffs
Shoreline platforms

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3
Q

Name a high energy environment

A

Coasts facing the Atlantic where the waves are powerful all year - Cornwall

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4
Q

What is a low energy coastline?

A

Coasts where the waves are less powerful or where the coast is sheltered from large waves
The rate of deposition exceeds the rate of erosion
Sandy and estuarine coasts found

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5
Q

What are some landforms that are created in low energy environments?

A

Beaches
Spits
Coastal plains

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6
Q

What is the coastal system?

A

The process of the changing coastline which is constant

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7
Q

Inputs for the coastal system

A

Marine - waves, tides, storm surges
Atmospheric - weather, climate
Terrestrial - Rock type, structure, tectonic activity
People - human activity, coastal management

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8
Q

Processes at the coastal system

A 
Weathering 
Mass movement 
Erosion 
Transport 
Deposition
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9
Q

Outputs at the coastal system

A

Erosional landforms
Depositional landforms
Types of coasts

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10
Q

Structure of land in north and west

A 
Rocky coasts 
harder older rock 
resistant to Atlantic erosion 
rocky coastline can withstand storms 
High energy coastlines
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11
Q

Types of rocks in the north and west

A

Igneous rock - basalt and granite
Older compacted sedimentary rocks - old red sandstone
metamorphic rocks - slates and schists

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12
Q

Structure of land in south and east

A

Weaker and younger sedimentary rocks - chalk, clay, sandstone
Mostly low lying sanding beaches
Low energy environments

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13
Q

Example of coastal plain

A

The Wash - area of low, flat relief
Largest estuary in UK
Tidal creeks, mudflats, salt marshes, lagoons

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14
Q

Littoral zone

A

the boundary between the land and sea

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15
Q

Order of littoral zone - land to sea

A

Back shore, foreshore, near shore, offshore

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16
Q

Which area of the littoral zone are effected the most?

A

Back shore and foreshore - They experience the most changes as it is where the most human activity occurs

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17
Q

Back shore

A

usually above influence of waves

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18
Q

Foreshore

A

Inter-tidal or surf zone

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19
Q

Nearshore

A

Breaker zone - zone of breaking waves

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20
Q

Offshore

A

Beyond influence of waves

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21
Q

Why is the littoral zone constantly changing?

A

due to dynamic interaction between sea processes

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22
Q

Long term factors of changing littoral zone

A

Changes in sea level

Climate change

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23
Q

short term factors of changing littoral zone

A

Individual waves
daily tides
seasonal storms

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24
Q

How can be coasts classified?

A

Geology
Formation processes
Balance of erosion and deposition
Sea level change

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25
Q

How can be coasts classified? - geology

A

Rock type and structure can create rocky/sandy/concordant/discordant

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26
Q

How can be coasts classified? - formation processes

A

Primary coasts - land based processes (river deposition)

Secondary coasts - marine based processes (wave action)

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27
Q

How can be coasts classified? - balance of erosion and deposition

A

Erosional or depsotional coasts

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28
Q

How can be coasts classified? - sea level change

A

submergent or emergent

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29
Q

Different sediment supplies

A

Cliff eroding
tidal current which picks up glacial deposits from shallow sea floor
from other coasts
Rivers discharge into coastal area

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30
Q

Sediment cells

A

Created when sediment comes from two directions from North and East

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31
Q

Strata

A

layers of rock

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32
Q

Bedding planes

A

These are natural breaks in strata, caused by gaps in time during periods of rock formation (horizontal cracks)

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33
Q

Joints

A

These are fractures, caused either by contraction as sediments dry out or by earth movements during vertical uplift

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34
Q

Folds

A

Formed by pressure during tectonic activity, makes rocks buckle and crumple

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35
Q

Faults

A

Formed when stress or pressure to which a rock is subjected, exceeds its internal strength, causing it to fracture - the faults then move or slips along fault plains

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36
Q

dip

A

the refers to the angle which strata lie - horizontally, vertically, dipping towards or away from sea

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37
Q

Cliff profiles - marine erosion dominated characteristics

A

Steep face
Active undercutting
Limited cliff base debris - as it is quickly broken up by erosion and carried away by waves
unvegetated

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38
Q

Cliff profiles - sub-aerial processes dominated characteristics

A

Shallower curved slope profile, lower relief
low angle
accumulated debris
sub-aerial processes of surface run-off erosion and mass movement
debris not removed due to low marine wave erosion

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39
Q

Cliff profile

A

The height and angle of a cliff as well as its features, such as wave-cut notches or changes in slope angle

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40
Q

Characteristics of a coast with cliffs

A

Transition from land to sea is abrupt
Low tide = foreshore is exposed as a rocky platform
cliffs are vertical

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41
Q

Characteristics of sandy coastline

A

High tide = beach is inundated, vegetated dunes aren’t

Dune vegetation stabilises the coast and prevents erosion

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42
Q

Characteristics of estuarine coastline

A 
Found at the mouth of rivers 
extensive mudflats, cut by channels 
Low tide = exposed
High tide = inundated 
Back shore's mudflats are vegetated 
Coastline transitions from land to sea
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43
Q

Geological structure

A

Refers to how the rock is arranged on macro scale. it looks at the arrangement of different rock types in relation to each other

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44
Q

Concordant coastline

A

Rock is parallel to the coastline

Straight coast with development of coves

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45
Q

Discordance coastline

A

Rock is perpendicular to coastline

Headlands and bays

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46
Q

Explain how headlands and bays are formed

A

Discordant coastline there are layers of hard and soft rock perpendicular
wave action erodes less resistant rock quick due to abrasion and HA = bays
More resistant rock is left = headlands - this causes incoming waves to refract as water becomes shallower (wave refraction)
wave energy is now concentrated on the headland
wave becomes higher and steeper increasing erosional power
bay is sheltered as wave energy dissipated - beaches form

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47
Q

In theory what may happen overtime to headlands and bays?

A

Headlands will be eroded to become caves, arches, stacks. The coastline may even out before the process starts again

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48
Q

Coastal morphology

A

The shape and form of coastal landscapes and their features

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49
Q

Coastal recession

A

Coastal erosion

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50
Q

Horizontal starta creates..

A

steep cliffs
-recession rates are quicker when soft layer bottom
cliff retreat is exposed to the sea
fairly stable profile

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51
Q

cliff profile - rock dips gently towards the sea, almost vertical points

A

joints opened up by pressure and release and weathering

slight seaward dipping bedding planes can increase recession rates due to mass movement and weathering

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52
Q

cliff profile - steep dips towards sea

A

rock slabs slide down the cliff along bedding planes

seaward dipping bedding planes can be unstable this increases recession rates

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53
Q

cliff profile - rocks dip inland producing a stable, steep cliff profile

A

landward dipping bedding plane
steep and stable
this can decrease recession rates

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54
Q

cliff profile - rock dips inland but with well-developed joints at right angles to bedding planes

A

joints act as slide planes - this can increase recession

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55
Q

meso

A

medium

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56
Q

micro

A

small

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57
Q

macro

A

large

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58
Q

Geological structure on meso scale

A

sedimentary tend to be in clear defined layers

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59
Q

Geological structure on micro scale

A

some rock types are more likely to have joints and bedding planes

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60
Q

Most resistant rocks (igneous)

A

crystalline structure - interlocking crystals
-well-connected, impermeable, joints
create rocky coastlines with steep cliff profiles that erode slowly
igneous rocks like granite recession rates = 0.1-0.3 cm/yr

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61
Q

Resistant metamorphic rocks

A

well connected and impermeable
folded and faulted so have weaknesses
create rocky coastlines with steep cliff profiles
marble, schist, slate erosion rates = 0.5-1cm/yr

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62
Q

Resistant sedimentrey rock

A

limestone and chalk are relatively resistant but are more vulnerable as they are clastic
-made up of cemented sediment particles rather than interlocking crystals
-formed in strata with joints providing weaknesses and makes limestone permeable
chalk is porous as there are air spaces between particles
Form steep cliffs, headlands and wave-cut platforms
LS = 1-2cm/yr
chalk = 1-100cm/yr

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63
Q

Less resistant rocks - unconsolidated

A

often layers of impermeable rock where water can remove cement between particles
high pore water pressure can reduce stability
unconsolidated rocks have not been cemented together by pressure
sandstone = 10-100cm/yr
boulder clay - left by glaciers - least resistant as it is lose and not cemented together = 100-1000cm/yr
stepped/slumped coastlines due to slumping

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64
Q

Factors affecting the rate of coastal recession

A

Geology and lithology
weathering and mass movement
wave energy
absence of beach
rising sea levels
human intervention - coastal management, development
marine processes- fetch, destructive waves, lsd, sub aerial processes

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65
Q

How are coves formed?

A 
concordant coastline - waves are parallel to sea 
destructive waves 
destructive waves hit coastline in winter - HA and abrasion 
attacks weaknesses (joints and faults) in resistant limestone
eventually erosion slows down as more resistant chalk layers are met and cove has been made.
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66
Q

Dalmatian coasts

A

tectonic activity folded limestone layers so that ridges (anticlines) and valleys (synclines) formed parallel to the coast
Sea level rose due to end of ice age and drowned the valleys creating a submergent coastline
The ridges remain as islands running parallel to the coastline

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67
Q

Haff coasts

A

Form on concordant coastlines
Long sediment ridges topped by sand dunes that run parallel to the coast
The build of these sand dunes have created lagoons between them and the shore
Form in low energy environments where deposition occurs but onshore winds and low energy waves
- Baltic Sea

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68
Q

factors affecting shape of the coastline

A

rocks and sediment

vegetation

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69
Q

How does vegetation help stabilise unconsolidated sediments at the coast and reduce erosion?

A

Marram Grass - xerophyte

Glasswort - halophyte

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70
Q

How do Marram Grass stabilise sediment?

A

Deep roots
Capture blown sand making it ideal for stabilising shifting dunes
Growing conditions

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71
Q

How do Marram Grass stabilise sediment? - deep roots

A 
3m deep roots help to bind sediment together making them less vulnerable to wind and water erosion - they reach down in search of moisture 
creeping stems (rhizomes) extend widthways, sending down even more like ladder structures
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72
Q

How do Marram Grass stabilise sediment? - growing conditions

A

Grows in conditions, free-draining sand - helps to prevent unnecessary water loss

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73
Q

where are marram grass?

A

sand dunes - xerophytes

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74
Q

Where are glasswort?

A

salt marsh - halophyte

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75
Q

How do Glasswort stabilise sediment?

A
  • submerged
  • stem
  • dead organic matter
  • salt resistant
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76
Q

How do Glasswort stabilise sediment? - submerged

A

-when submerged, plants provide a protective layer so that the sediment is not directly exposed to erosion by the tide

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77
Q

How do Glasswort stabilise sediment? - stem

A

it has a succulent stem so it stores water

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78
Q

How do Glasswort stabilise sediment? - dead organic matter

A

dead organic matter is added to the sediment and helps to create soil which is less vulnerable than loose sediment

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79
Q

How do Glasswort stabilise sediment? - salt

A

salt resistant - protected against water erosion

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80
Q

sand dune

A

psammosere

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81
Q

Salt marsh

A

halosere

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82
Q

Succession

A

refers to the changing structure of a plant community over time as an initially bare surface is colonised by pioneer species and continues to develop

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83
Q

What kind of coastlines does plant succession occur on?

A

coastlines where deposition takes place

low energy environments that are sheltered from high energy waves

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84
Q

Fetch

A

the distance over which the wind has blown

- south coast has the largest fetch (Devon and Cornwall)

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85
Q

How are waves created?

A

As wind blows over the ocean, friction occurs and energy is transferred to create a wave
The stronger the wind = the greater the wave power

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86
Q

What factors affect the energy of waves?

A

wind speed
distance
time
fetch

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87
Q

As the wave gets closer to the shore…

A

the wave length decreases

the wave height increases

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88
Q

Describe the movement of the wave

A

Waves move across the open ocean in a circular motion as ocean swell
As they reach shallower water, the frictional drag on the sea bed slows down the base of the wave
Eventually the wave breaks as the top of the wave is moving faster than the base

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89
Q

What is a swell wave?

A

is an ocean waves system raised at some distance away due winds blowing there

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90
Q

Where are swell waves formed?

A

Travel out of a stormy or windy area that have travelled from their fetch and continue on in the direction of the winds that originally formed them as sea waves

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91
Q

What happens as the swell advances?

A

its crest becomes flattened and rounded, smoothed surface

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92
Q

Do swell waves follow the prevailing winds?

A

They come from different directions than normal prevailing winds and sea waves
Sometimes come from the same direction making it hard to distinguish the two different systems

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93
Q

When is marine erosion at its highest?

A

Winter season as they produce destructive waves

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94
Q

What are landforms of coastal erosion?

A 
Headlands and bays 
Coves 
Caves, arches 
Cliffs 
Blowholes
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95
Q

Simple - how are cave, arch, stack, stump formed?

Example

A

Wave refraction concentrates wave action on the headland
Hydraulic action and abrasion slowly erode the headland to form a series of headland
e.g. Old Harry’s Rock
more on folder

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96
Q

Simple - how are blowholes created?

A

Caves can potentially collapse to produce a hole in the cliff
Waves hitting the base of the cliff can be forced through and spout water at the top

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97
Q

How are wave cut platforms formed?

A
  • wave action at the base of the cliff means that hydraulic action and abrasion undercuts the cliff to form a wave cut notch
  • continues and the cliff above the notch is left unsupported and eventually collapses
  • cliff retreats leaving wave cut platform which is the base of the cliff that is left
  • this process maintains steep cliff profiles
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98
Q

Beach morphology

A

the shape of a beach, including width and slope profiles and other features such as berms

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99
Q

Beach morphology - What happens to it during summer?

A

Deposition exceeds erosion
Creation of a berm
Slopes
during summer, sediment is returned by constructive waves

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100
Q

Beach morphology - What happens to it during winter?

A 
Erosion exceeds deposition 
Dune erosion 
Berm erosion 
Bar formation 
Steep cliff 
during winter, sediment is dragged offshore by destructive waves
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101
Q

Beach morphology - how does material change along a beach?

A
  • beaches consist of lose material so morphology changes as waves change
  • material along a beach profile also varies in size and type depending on distance from the shoreline
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102
Q

Describe a beach profile in summer

A
  • beach is steeper when there are more constructive waves
  • constructive waves are less frequent (6-9 per min) so wave energy dissipates and deposits over a wide area
  • the swash of constructive waves deposits larger material at the top of the beach creating a berm
  • as the berm builds up, the backwash becomes weaker due to draining through percolation rather than down the beach
  • beach material becomes smaller towards the shoreline
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103
Q

Describe a beach profile in winter

A
  • Destructive waves occur at a higher frequency
  • berms are eroded by plunging waves and high energy swash
  • strong backwash transports sediments offshore depositing it as offshore bars
  • sometimes the backwash exerts a current known as a rip or undertow
  • this drags the sediment back as the next wave arrives over the top
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104
Q

What are the factors that influence beach morphology?

A
  • Sediment supply from river is reduced
  • Interference in sediment supply along the coast
  • Climate change
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105
Q

What are the factors that influence beach morphology? - Sediment supply from river is reduced

A

Due to construction of dams on rivers that traps sediment upstream

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106
Q

What are the factors that influence beach morphology? - Interference in sediment supply along the coast

A

Coastal management

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107
Q

What are the factors that influence beach morphology? - Climate change

A

increase in storms, destructive waves, erosion

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108
Q

Beach profile in storm beaches

A

high-energy deposition of very coarse sediment

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109
Q

Beach profile in the middle of beach

A

mostly sand but sand is more coarser where berms/ridges have been deposited than in channels or runnels

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110
Q

Beach profile of offshore

A

offshore ridges and bars are formed by destructive waves erosion and subsequent deposition of sand and shingle offshore

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111
Q

Cavitation

A

causes air in cracks to expand and forces cracks open

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112
Q

Why is sediment constantly moving? 3 factors

A

waves, tides and currents
LSD
traction, saltation, suspension

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113
Q

Traction

A

large sediment rolled across seabed

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114
Q

Saltation

A

Medium load bounced

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115
Q

Suspension

A

Fine load taken along

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116
Q

Describe the process of long-shore drift

A
  • prevailing winds approach coast at an angle
  • swash moves sediment up beach at 45degrees and backwash moves 90 degrees down under gravity
  • traction, saltation and suspension
  • sediment is moves east and over time a drift aligned beach is formed
  • sediment experiences attrition and abrasion becomes smaller and more rounded
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117
Q

What is a swash aligned beach?

A
  • waves approach the coastline perpendicular to the beach

- the swash and backwash move sediments up and down the beach creating a stable and straight beach

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118
Q

What is a drift aligned beach?

A
  • waves approach at an angle and sediment is moved along by long-shore drift
  • creates wide beaches but uneven sediment spread
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119
Q

What are the sources of sediment?

A
  • rivers
  • constructive waves from seabed
  • cliff erosion
  • LSD transports sediment
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120
Q

Why does deposition occur?

A
  • deposition in low energy coastal environments occur due to gravity
  • coarse sediment drops first, finer is further away
  • flocculation helps deposition of fine clay particles that are very light
  • these clump together in salt water making them heavier
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121
Q

What stabilises deposited sediment?

A

Vegetation - salt marsh, sand dune succession

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122
Q

Describe the formation of a spit

A
  • lsd moves sediment along
  • lsd continues as there is a change in the direction of the coastline
  • waves lose energy in the slacker behind the headland and large sediments are deposited
  • as deposition occurs, spit forms
  • finer material is carried further along the spit before being deposited as it is lighter
  • flocculation helps to settle fine clay
  • when the rivers current stops deposition across the estuary preventing a bar from forming
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123
Q

What happens when there is no river currents during the formation of a spit?

A

when there is no river currents preventing long shore drift depositing in a straight line across so the spit eventually joins the land to create a bar

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124
Q

Example of a spit

A

Spurn head, Chesil Beach

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125
Q

Example of a bar

A

Slapton Sands, Devon

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126
Q

Describe the formation of a tombolo

A
  • an island joined to the mainland
  • it develops when deposition occurs behind an island due to the low energy environment
  • eventually the island becomes connected to the mainland
  • also by lsd and a bar forming
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127
Q

Example of a tombolo

A

St Michaels mount, Cornwall/ Chesil Beach

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128
Q

Describe how double spits and cuspate forelands are formed

A
  • LSD happens from both directions, leading to 2 spits forming and meeting up -cuspate forelands
  • deposition occurs in the slack water behind to create the distinctive shaped coastline
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129
Q

Examples of double spits and cuspate forelands

A

Dungeness, Kent

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130
Q

Describe how barrier islands are formed

A
  • an offshore sand bar thought to have formed when a plentiful supply of sediment was deposited in sand dunes along the eastern seaboard of the USA by waves and winds
  • as sea levels have risen, land behind was flooded to create a lagoon but the sand dunes themselves become elongated islands running parallel to the coast in USA
  • as sea levels rise, they migrate inland
  • they provide protection to the coastline during storms as they absorb wave energy
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131
Q

Describe how offshore bars are formed

A
  • a long ridge of sand and pebbles found a short distance out to sea
  • forms in shallow water offshore where slope is gentle
  • following a large erosion event during a storm
  • beach and sand dunes can be scoured heavily by destructive waves
  • extra sediment is deposited vertically offshore in a bar
  • these offshore bars may only be temporary
  • LSD can add to them or change their shape
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132
Q

Sediment cell

A

an area of a coastline that acts like a closed system

-there are sources, transfers and sinks within each cell

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133
Q

How many cells is the Uk split into?

what are cells?

A

11 sediment cells
length of the coastline that are relatively self contained boundaries which are often natural boundaries e.g. headlands
-each sediment cell is clones when there are large barriers between them with little transfer between them

134
Q

What are cells split into?

A

split into sub cells
they are managed at a local level by an SMP (shoreline management plan)
-under certain conditions transfers between the main sediment within the cell takes place

135
Q

Name the sources of the cell system

A
  • wind-blown sediments from land
  • erosion of cliffs
  • onshore currents supplying sediments to the shore
  • land sediments eroded by rivers
  • sub-aerial processes (weathering and mass movement)
  • shells and remains of marine organisms
136
Q

Name the transfers of the cell system

A 
LSD
wave transport  - swash and backwash 
tides moving in and out 
currents- localised (rip) or large scale 
wind along shore or on/offshore
137
Q

Name the sinks of the cell system

A 
Sand dunes 
Offshore bar 
back depositional landforms 
Foreshore depositional landforms 
nearshore depositional landforms 
offshore sediment deposition to deep offshore water
138
Q

what is a sediment budget used for and why are they useful?

A
  • the amount of sediment gained from sources and lost to sinks can be and called a sediment budget
  • they are useful in assessing coastal change and the effects of coastal management schemes
139
Q

What is a sediment budget?

A

the amount of sediment gained from sources and lost to sinks can be quantified
inputs from sources - outputs to sinks

140
Q

What happens if the sediment budget is negative?

A

The coastline starts to degrade - erosion

141
Q

What happens if the sediment budget is positive?

A

The coastline starts to aggrade - accretion

142
Q

What happens if the sediment budget falls?

A

There is more loss to sinks that gained from sources

Therefore there may be more erosion from sources to balance the budget

143
Q

What happens if the sediment budget increases?

A

There is more gain from sources then loss to sinks

Therefore more deposition in sinks

144
Q

What state are sediment cell systems in?

A

in a state of dynamic equilibrium

145
Q

What is negative feedback?

A

Usually helps to maintain a balance within the system

146
Q

Example of negative feedback?

A

E.g. Wave erosion causing rocks falls which then protects the base of a cliff from further erosion

147
Q

What is positive feedback?

A

Works to increase the erosion of coast and increases the source of sediment

148
Q

Example of positive feedback?

A

E.g. Damage to sand dunes during storm conditions, which may create a ‘blow out’ allowing the wind to move sand away, preventing grass from regrowing, therefore further erosion occurs

149
Q

How has the Holderness Coastline in Northern England been affected by climate change?

A
  • storms in a year can remove 7-10m of coastline
  • weak clay, stormy nature of the North Se, rising sea levels of 4mm a year
  • slumping
150
Q

Sub aerial processes

A

refers to the processes of weathering and mass movement

-processes that occur on the cliff face rather than the cliff foot

151
Q

What is weathering?

A

the breakdown of rock in situ by mechanical, chemical or biological agents

152
Q

What is erosion?

A

the breakdown and removal of rock by an external agent (wind, waves, rivers, ice)

153
Q

What is mass movement?

A

the movement of rocks/sediment downslope due to gravity - weathering processes can help this happen

154
Q

What factors might influence how vulnerable a cliff is to mass movement?

A
  • lithology and structure of a cliff can determine which mass movement it is vulnerable to
  • weathering processes can contribute to the loosening of cliff faces so that mass movements are more likely
  • rainfall is often a cause of mass movements
  • angle of the slope
155
Q

Name the different types of mass movement

A 
Landslide
Slump
Mud/earth flow 
Rock fall
Debris slide
Soil creep
156
Q

Describe how a landslide occurs

A

Rocks that are jointed or have bedding planes that are parallel to slope or cliff surface are susceptible to mass movement
-increase water, lack of friction will increase sliding

157
Q

Describe how slumps occur

A

Occur is saturated conditions

  • rotational movement
  • moderate/steep slopes
  • soft materials (clay and sand) overlies more permeable rock which causes rotational scars
  • repeated slumping creates a terrace cliff profile
158
Q

Describe how mud/earth-flows occur

A

increase in water can reduce friction causes earth and mud to flow under the underlying bedrock

159
Q

Describe how rocks falls/ debris slides occur

A
  • occur on strong joints rock faces which are exposed to mechanical weathering
  • occurs on slopes over 40 degrees
  • material bounces or falls vertically to form scree/talus
160
Q

Describe how soil creep occurs

A
  • very slow downhill movement of individual particles
  • continuous process
  • slowest form of mass movement
161
Q

What is a eustatic sea level rise?

A

When the sea rises and falls by itself
-sea changes relative to land (global) as ice melts from ice caps and glaciers and thermal expansion or forms according to global climate and the cycle glaciers or inter-glaciers

162
Q

What creates a eustatic sea level rise?

A

tides
ice ages
storm surges
hurricanes

163
Q

What creates an isotonic sea level rise?

A

when the land changes relative to the sea

-the land rises and falls by itself (local)

164
Q

what creates a eustatic sea level rise?

A

Isotonic rebound - large amounts of ice pressed down on land in the last ice age and now these land masses are rising

165
Q

What is an isotonic rebound?

A

large amounts of ice pressed down on land in the last ice age and now these land masses are rising - glacial rebound

166
Q

In relation to the tees - ex line, where is the low land and is it rising or sinking isotonically?

A

The lowland in the UK is sinking, this is the South and East UK

167
Q

In relation to the tees - ex line, where is the highland and is it rising or sinking isotonically?

A

The highland in the UK is rising, this is the North and West UK

168
Q

What factors affect sea level?

A

Tectonics
Accretion
Sub-mergent coastline
Emergent coastline

169
Q

How do tectonics affect the sea level?

A

land can be pushed by plates in a series of earthquakes

  • new islands can rise out of the sea in eruptions
    e. g. Surtsey, Iceland
170
Q

How does accretion affect sea level?

A

this is the deposition of sediment

  • in a river estuary or delta, this can weigh down the crust and also causes sinking (subsidence)
    e. g. Thames estuary
171
Q

How does a submergent coastline affect sea level?

examples

A

It is produced by a eustatcic sea level rise

e.g. Fjords, Rias, Dalmatian coasts

172
Q

How does an emergent coastline affect the sea level?

A

produced mainly by isotonic readjustment/rebound
includes relict/fossil cliffs and raised beaches
e.g. Vik, South Devon

173
Q

What are fjords?

A

they are drowned glacial u shaped valleys

174
Q

how are fjords formed?

A
  • large glaciers formed huge u-shaped valleys during the ice age that went well all the way into the sea
  • the erosive power of the ice eroded deeper then sea level
  • at the end of the ice age, eustatic sea level rise drowned the valleys to create spectacular fjords
  • have a submerged lip at the Seward end of the fjord where the glacier need and left a terminal moraine
  • post glacial isostatic rebound is occurring in many areas where fjords are present, slowly lifting them up from sea level, making them shallower by a few mm a year
175
Q

what are rias?

A

drowned river valleys that were not glaciated in the last ice age.

176
Q

how are rias formed?

A
  • before the end of the last ice age, a small river with its tributaries met the sea
  • when sea levels rose eustatically, the main channels and its tributaries and the floodplain were drowned and the sea advanced inland
  • this created an estuary at the mouth that is larger than the original river valley
177
Q

How are emergent coastlines formed?

A
  • at the end of the last ice age, the ice melted and the land that was covered started to rebound slowly as the huge weight was removed
  • this meant that beach platforms rose out of the sea to become new land (raised beaches) and their cliffs also rose to become stranded above the current sea level
  • as the raised beach is no longer a beach, sediment is slowly removed by wind, rain and rivers
  • the relit cliff may still display features like caves and stacks
178
Q

What does IPCC stand for?

A

Intergovernmental panel on climate change

179
Q

What is IPCC?

A

an international organisation of scientists, created by the united nations, from around the world who monitor climate change and creates climate models

180
Q

What are the two main causes of sea level rise?

A
  • as water heats up, it takes up more room

- as glaciers and ice sheets are melted extra water is added to the ocean (Greenland, Antartica, mountain glaciers)

181
Q

How are greenhouse gases affecting sea level rise?

A

over 90% of heat trapped by greenhouse gases is being absorbed by the oceans, this makes water expand which results in sea level rise

182
Q

How have sea levels changed around the world?

A
  • Globally, sea levels have risen by 6cm
  • doesn’t happen at the same speed everywhere
  • most places have seen a rise in sea level
  • few places have seen a fall in sea level - waters have been cooling due to pacific decadal oscillation e.g. The Gulf stream, West Coast USA
  • Western Pacific sea levels have been rising very rapidly due to the heat being pushed from east to west across the Pacific
183
Q

What contributes to sea level rise?

A
  • thermal expansion (40% so far)
  • melting of glaciers e.g. Alps,Himalayas, Andes (27% so far)
  • melting of major ice sheets e.g. Antarctic (10%), Greenland (15%)
184
Q

Why is there a debate about how much sea levels will rise?

A
  • unclear about how much temperatures will rise and therefore how much thermal expansion
  • unclear to how rapidly the ice sheets will melt - Greenland ice sheet is more vulnerable than Antarctic as it is smaller and is not as close to the pole
185
Q

Where is most at risk of sea level rise?

A

Low-lying areas - The Maldives, Bangladesh, Netherlands

Coastal Cities - New York, Southampton, Mumbai, Tokyo, Miami

186
Q

What melts to create higher sea levels?

A
  • glaciers, ice caps, ice sheets, thaws permafrost

- more water is added to the oceans which creates a sea level rise

187
Q

What is thermal expansion?

A

As seawater heats up by absorbing heat fro the atmosphere its volume expands

188
Q

What have the IPCC projected?

A

-the projected rate of sea level rise is between 8-16mm per year

189
Q

What impacts will further sea level rise have?

A
  • wave heights will increase in the Arctic Ocean as sea ice melts, increasing wave erosion on Arctic coasts
  • stormier seas - stronger storms such as mid-latitude depressions creating larger, more destructive waves
  • these plus higher sea level rates makes it easy to predict that erosion rates and coastal change in general will increase in the future
190
Q

Coastal flood risk

A

the risk or likelihood of flooding taking place at the coast

191
Q

What are the factors influencing flood risk at the coast?

A
  • eustatic sea level rise - caused by global warming
  • dams
  • population increase at the coast
  • destruction of mangrove forests
  • low-lying land
  • shape of the coast
  • groundwater extraction
  • isotonic sinking
  • global warming
192
Q

How does eustatic sea level rise caused by global warming influence flood risk at the coast?

A
  • it is predicted by IPCC that sea level will rise to be 28-98cm by 2100
  • human and global
193
Q

How does dams influence flood risk at the coast?

A

-block sediment getting to deltas to replace what is lost by erosion
local and human

194
Q

How does population increase at the coast influence flood risk at the coast?

A
  • by 2060, 12% will live in low elevation coastal areas
  • this increases demand for water extraction which leads to more risk
  • global and human
195
Q

How does destruction of mangrove forests influence flood risk at the coast?

A
  • this is done to provide wood and charcoal however it leaves the coast exposed to erosion
  • mangroves can reduce wave heights by 40%, stabilises sediment and reduces storm surge height
  • local and physical
196
Q

How does low-lying land influence flood risk at the coast?

A
  • especially islands like the Maldives and deltas like the Ganges and The Nile
  • local and physical
197
Q

How does the shape of the coast in Benegal influence flood risk at the coast?

A

The North Sea and the bay of Bengal
-the coast narrows, acting as a funnel for weather systems, increasing storm surges heights which is called the fuelling effect

198
Q

How does groundwater extraction influence flood risk at the coast?

A

-can cause subsidence of land at the coast

199
Q

How does isotonic sinking influence flood risk at the coast?

A

-causing south eastern Britain to sink

200
Q

How does global warming influence flood risk at the coast?

A

-evidence that this will increase wind speeds, wave heights, frequency of storm surges and the magnitude of tropical storms

201
Q

How does a storm surge form?

A
  • low pressure weather event (depression) creates a bulge in the sea
  • strong winds arrives a pushes the bulge towards the coast
  • land topography can funnel the sea, increasing the height further
  • high tides can also increase the height
  • sea level rushes onto land as a surge
202
Q

What are the elements for a storm surge to occur?

A
  • low air pressure - zone of rising air that creates rain clouds
  • strong winds
  • very high tides
203
Q

How have methods of measuring erosion changed through time?

A
  • posts in the ground were used as reference points before GPS was invented in the 1990s
  • old maps are used to look at changes before this
  • Now LIDAR is used in combo with GPS
204
Q

What does LIDAR stand for?

A

Lights detection and ranging

205
Q

What is LIDAR?

A

A land bases laser scanner that takes several scans and combines information with GPS (Global positioning system/satellite

206
Q

How does LIDAR work?

A
  • equipment is set up on the beach in front of the eroding cliff line from at a distance of 100-150m
  • it scans a swathe of cliff up to 800m in width, collecting 2000 individual measurements of the cliff per minute
  • data collected in the filed by laser scanning and GPS are entered into a modelling package which calculates cliff top recession rates
207
Q

Physical factors causing coastal erosion

A
  • geology of coast
  • marine processes
  • subaerial processes
  • tides
  • wind direction
  • weather systems
208
Q

Human factors causing coastal erosion

A
  • coastal defences

- offshore dredging

209
Q

Case Study: What happened to Hallsands Village?

Which topic does this relate to?

A
  • a storm ripped apart the village in 1917 because of the villages natural shingle beach defence was dredged in the 1890s out to create a new navel dock in Plymouth and there was nothing to dissipate the energy
  • relates to what factors contribute to coastal recession
210
Q

What are the social impacts of coastal flooding and recession?

A
  • deaths
  • health - stress and worry
  • bereavement
  • amenity value
211
Q

What are the economic impacts of coastal flooding and recession?

A
  • loss of property
  • loss of businesses
  • damage to infrastructure
212
Q

What are the environmental impacts of coastal flooding and recession?

A

-loss of coastal ecosystems and habitats

213
Q

Examples of social impacts of coastal flooding and recession

-environmental refugees

A

-environmental refugees will be created in greater numbers as sea levels continue to rise and takes peoples homes
-developed countries need to offer their help to
environmental refugees from less developed countries
e.g - New Zealand has accepted 3000 people from Tuvalu as part of a labour migration plan
-most of the land in Tuvalu and the Maldives is only 2-3m above sea level

214
Q

Examples of environmental impacts of coastal flooding and recession
-fragile ecosystems

A
  • as sea levels rise, salt water will be pushed higher up estuaries and damage fragile ecosystems
    e. g. The Great Barrier Reef, Australia could perish as sea levels rise as they require a certain amount of light for photosynthesis
215
Q

Examples of economic impacts of coastal flooding and recession
-environmental refugees

A

e. g. South Devon main railway line at Dawlish was destroyed in Feb 2014 by severe coastal storms £35m
e. g. the collapse of Holberk Hall Hotel in Scarborough 1993 after 2 months of heavy rainfall - no compensation was received
- homeowners on the Norfolk coastline have properties worth £1
- property insurance in the UK does not cover loss from coastal erosion - there is no compensation provided by the government

216
Q

What is a refugee?

A

is someone seeking safety in another country due to fear of persecution in their own country

217
Q

Sustainable

A

meeting the needs of today’s coastal areas as well as those of the future

218
Q

What is a major factor they need to consider when using sustainable coastal management?

A

-future sea level rise and erosion means adaptation in the best way to minimise impacts is the best way forward

219
Q

Should coastlines be managed as a whole or in sections?

A

-better as a whole, taking into consideration each littoral cell and how they interlink (ICZM)

220
Q

What kind of sustainable coastal management strategies could be used to help manage and adapt?

A
  • educating communities on change
  • monitoring coastal change
  • creating alternative livelihoods
  • managed retreat and soft engineering
221
Q

What is sustainable management?

A

a long-term approach that considers future threats such as sea level rise and storm surges
-can sometimes result in the abandonment of coastline areas e.g. Island States or lowland areas

222
Q

Why are their some conflicts with local people with sustainable coastal management?

A
  • can sometimes result in the abandonment of coastline areas
  • this will conflict with the wishes of local people who may lose their; land, home, job and sense of community
  • may feel their is no social justice
223
Q

What affects the coastal land?

A
  • physical processes operating in a littoral cell which are interlinked for long stretches of the coast
  • human activities
224
Q

What factors need to be considered when managing coasts?

A
  • the long length of coastline
  • all stakeholders
  • long timescale (physical processes can take 100s of years)
225
Q

What does ICZM stand for?

A

integrated coastal zone management

226
Q

What are the aims of ICZM?

A
  • conservation of coastal ecosystems
  • ensuring the ability of future generations to use the coast
  • involvement of all stakeholders
227
Q

What is the ICZM?

A

A systems perspective recognises that an action in one location is likely to have an impact elsewhere. The development of ICZM plans takes this as a basis for holistic (all components taken into account) planning.

228
Q

Physical factors affecting coastal retreat

A
  • geology of the coast
  • marine processes
  • sub-aerial processes
229
Q

When will the most rapid retreat occur?

A

Where there are weakly consolidated rocks, large destructive waves, submergence of the coastline, large scale mass movements and constant weathering processes

230
Q

What factors cause slow rates of recession?

A
  • resistant rocks
  • smaller constructive waves
  • little mass movements
  • slow weathering processes
231
Q

What are the human factors that affect coastal recession?

A
  • coastal defences

- offshore dredging

232
Q

What are the human factors that affect coastal recession?

  • coastal defences
  • example
A
  • built at one location will init the supply of sediment cell, this results in the coast further along won’t receive beach building sediment
  • when supply is cut off, the beach gets narrower which means it is less able to absorb wave energy which allows the waves to hit back-shore with more force
  • e.g. Dunwhich, South of Southwold on Suffolk Coast
233
Q

What are the human factors that affect coastal recession?

  • offshore dredging
  • example
A
  • removes sand and gravel for construction purposes to deepen entrances of ports or to supply sediments for beach nourishment
  • deeper water caused by dredging allow waves to maintain their circular and energy closer inshore which as a destructive impact on the coast
234
Q

What impact does dredging have on the natural environment?

A
  • removes benthic species and communities
  • increases suspended sediment levels which damages coral reefs
  • sediments settling and covering sub-tidal and intertidal marine communities
  • increased deposition may raise sediment levels such as in estuaries
  • artificial deposition on beaches may offer sea level rise or isostatic sinking
  • local sea currents may be altered and waves may become much larger, affecting sediment balance and erosion rates
235
Q

How do sub-areal processes affect coastal retreat?

A
  • weathering weakens the rocks found at the coast and allows erosion rates to increase
  • mass movement moves sediments to the base of coastal slopes where wave action and longshore drift can carry material away
  • this then exposes the base of coastal slopes, resulting in cliffs retreating further
236
Q

How does rainwater have a direct impact on coastal slopes?

A

-creates rills and then gullies in unconsolidated materials or at weak points in harder rock

237
Q

How does wind direction affect coastal retreat?

A
  • changes daily and determines wave direction
  • strong winds = large waves
  • coasts will experience maximum erosion at these times and less when winds come from another direction
  • this links to fetch - the longer the fetch, the larger and more powerful the wave will be
  • coasts with longer fetches will retreat faster than those with shorter fetches
238
Q

What is fetch?

A
  • the distance from a coast across the ocean or sea to another coast
  • gives the max distance that a wave can travel uninterrupted
239
Q

What do high tides mean?

A
  • spring tides
  • occur hen the sun and the moon are aligned and so their total gravitational pull is at its strongest
  • at high tides, waves are more likely to be able to reach the back-shore and erode the land faster
  • if high tides coincide with destructive waves, erosion will be at a maximum.
240
Q

What do low tides mean?

A
  • neap tides

- occur when the sun and the moon are at right angles to each other and so their gravitational pull is at its weakest

241
Q

What are Perigean spring tides?

A

four times a year the moon is at its closest to the Earth and this creates slightly higher high tides

242
Q

Describe a high pressure weather system

A

calm conditions
smaller waves
anticyclones

243
Q

Describe a low pressure weather system

A
  • mixture of air masses at different temperatures
  • air rises rapidly
  • strong winds rotating on an anticlockwise direction
  • large waves created
244
Q

Describe the wave systems in winter

A
  • the difference between the temperature at the equator and the pole is at its greatest
  • means the depressions are at their strongest
  • with low air pressure and fast wind speeds
  • creates large destructive waves which results in fast recession rates
245
Q

How does global warming have an impact on weather systems?

A
  • has added more heat to the atmosphere - this has intensified the low-pressure systems
  • means that the UK now experiences even stronger winds and larger waves during these storm events
  • coastal erosion during winter is likely to increase, with recession being visible
246
Q

What does the IPCC report on how global warming will impact weather systems?

A

-reports that a 1cm rise in sea level will erode a beach by about 1m horizontally as the balance of processes is altered

247
Q

What is hard engineering?

A
  • the use of built structures
  • it aims to protect the coast by working against the forces of nature
    e. g. Groynes, Revetments, Rip Rap
248
Q

What is soft engineering?

A
  • makes use of natural systems such as beaches, sand dunes and salt marshes to help with coastal defence
    e. g. beach replenishment, offshore dredging
249
Q

Hard engineering examples

A 
groynes
revetments 
gabion 
rip rap 
recurved sea wall 
breakwaters
250
Q

Soft engineering examples

A
  • beach replenishment/nourishment
  • cliff regrading
  • cliff drainage
  • dune restoration
  • developing natural defences/managed retreat
251
Q

What are groynes? pros

A

wooden or rock structures that are along the beach at right angles fro the coast

  • they trap sediment moved by LSD and build up beach
  • beach absorbs energy and increases recreational value
252
Q

Cons of groynes

A
  • can starve areas down-drift of sediment
  • wood rots
  • rock is more expensive £1000 per linear metre
253
Q

What are revetments? pros

A

Wooden or rock ramps that line the coast

  • absorb wave energy
  • air spaces allow the backwash of the wave to drain away but the sediment is trapped behind, reducing removal by destructive waves
254
Q

Cons of revetments

A
  • wood rots
  • rock is more expensive £1500 per linear m
  • don’t cope well with powerful storm waves so need lots of maintenance
  • unsightly
  • reduces access to beach
255
Q

What are gabions? pros

A

Cages of small rocks, stacked to make a wall along the coast

  • absorbs wave energy
  • flexible as can be added in different places
  • easy to maintain
256
Q

cons of gabions

A
  • light weight so can be removed in storms
  • not suitable for high energy coasts
  • cages can break and spill contents
  • unsightly
257
Q

What is rip rap? pros

A

large boulders positioned along the coastline

  • large surface area so absorbs wave energy
  • can be used to hold back mass movements
258
Q

cons of rip rap

A
  • expensive including transport costs £50 per cubic m
  • can be. under scoured by strong backwash
  • can be moved in strong storms
  • unsightly, decreases access to beach
  • erosion occurs on back-shore in storms
259
Q

What is a recurved sea wall? pros

A

concrete barrier that is curved to reflect the waves and their energy

  • can be stepped to dissipate energy
  • tops used as promenades
  • long lasting
260
Q

Cons of recurved sea wall

A
  • most expensive £5000 per linear m
  • technical to build
  • foundations can be undermined - lsd or destructive waves
  • expensive to maintain
  • causes coastal squeeze
  • need deep foundations to prevent undercutting
261
Q

What are breakwater? pros

A
  • granite rock boulder dropped and aligned in short lengths in shallow offshore waters parallel to the coast
  • absorbs and dissipates waves before it reaches foreshore
  • created sheltered areas for recreation and boats
262
Q

cons of breakwater

A
  • expensive (1m -2m)
  • unsightly at low tide as geology does not match
  • may need further hard engineering
263
Q

What is beach replenishment? pros

A
  • sand Is dredged from the sea bed and pumped onto the beach to replenish it from the effects of LSD or destructive waves
  • the beach can be ‘reprofiled’ to recreate its original shape
  • large beach absorbs wave energy
  • natural looking
264
Q

cons of beach replenishment

A
  • need to be done every few years as lsd and destructive waves will continue to remove beach sediment
  • can disrupt marine ecosystem or the natural sediment cycling and deepening offshore so waves have more energy
  • expensive
265
Q

what is cliff regrading?

A

-engineers calculate a stable angle for the particular rock and the cliff is artificially cut back, changing its shape and reducing its angle to make it more stable

266
Q

cons of cliff regrading

A
  • very expensive £1m
  • unnatural
  • cliff line retreats into valuable land when constructed
  • not full proof in extreme conditions
  • needs agreement form land owners
267
Q

What is cliff drainage?

A

pipes built through it to take out the water that has percolated through it
-this prevents the cliff becoming saturated and therefore, it is less likely to slump

268
Q

cons of cliff damage

A
  • unsightly
  • can weaken the cliff when inserted
  • cannot prevent weathering or subsequent rock fall
  • difficult to insert enough without disturbing the cliff stability
269
Q

What is dune restoration?

A

Geotextile netting can reduce erosion but still allow water in

  • wooden structures erected vegetation planted to encourage sand deposition that builds up the dune
  • boardwalks made for people so they do no trample sand dunes
  • looks natural and protects ecosystems
270
Q

cons of dune restoration

A
  • only effective if public access controlled by fences and signs which reduces amenity value
  • strong storms can cause damage
271
Q

What is developing natural defences/managed retreat?

A
  • natural ecosystems such as sand dunes and salt marshes help to stabilise coastlines and act as natural buffers against SLR and storms
  • managed retreat also accepts that the coast is retreating by enhancing its natural defences, this can be slowed down
272
Q

cons of developing natural defences/managed retreat

A
  • needs agreement from land owners

- doesn’t prevent land from being lost

273
Q

What are the 4 management options for shoreline management?

A

do nothing
hold the line
advance the line
managed retreat/realignment

274
Q

do nothing

A
  • no active intervention

- meaning no investment will be made in coastal defences

275
Q

hold the line

A
  • trying to stop any further retreat of the coast

- involves a mixture of hard and soft engineering techniques

276
Q

advances the line

A
  • involves reclaiming the land and building out into the sea
  • may involve drainage as well as other hard engineering techniques
277
Q

managed retreat/realignment

example

A

removal of existing hard engineering defences and using more natural and sustainable techniques including protection, management or restoration of coastal ecosystems such as salt marshes and sand dunes
e.g. Abbots Hall Farm, Porlock Bay

278
Q

What needs to be considered before making management decisions?

A

CBA - Cost benefit analysis
EIA - Environmental impact analysis
Technical feasibility
Social and political factors

279
Q

What is a CBA?

A

Cost benefit analysis

  • a tool to help decide whether defending a coastline from erosion and or flooding is worth it
  • the value of the land vs the cost of the proposed management strategy
  • looks at the properties and the businesses that would ve lost
280
Q

What is an EIA?

A

Environmental impact analysis

  • short or long term positive and negative impacts on environment
    e. g. changes to flora and fauna, impacts on air and water quality
281
Q

What is technical feasibility?

A

it is not possible to hold the line in all areas

e.g. dynamic deposition features such as spits

282
Q

What are the social and political factors considered before management decisions?

A
  • impact and pressure on communities
  • campaigning and loss pf property, businesses
  • stress
283
Q

Why is a CBA controversial?

A
  • the value of a property is dependant on how at risk it is
  • human costs (worry and stress) and environmental costs (value of biodiversity and scenic beauty) are hard to quantify in financial terms
284
Q

What is the aim of EIA’s?

A
  • the aim is to identify the short term impact on the coastal environment of the construction
  • and the long term impacts of building new sea defences or changing a policy from hold the line to no active intervention
285
Q

What does an EIA include the assessment of?

A
  • impacts of water movement and sediment flow which can affect marine ecosystems due to changes in sediment load
  • impacts on water quality, which can affect sensitive marine species
  • changes to flora and fauna including marine plants, fish, shellfish, marine mammals
  • wider environmental impacts such as air quality, noise e pollution during construction
286
Q

How has offshore dredging affected Winterton-on-sea and Lowestoft? - case study for coastal retreat

A

Research by Marinet shows that offshore dredging between 6-19km out to sea has resulted in beach loss, undermining of sand dunes and erosion of wind farm cables and support at Scroby Sands

287
Q

How is Overstrand, North Norfolk being managed? - coastal retreat

A
  • a full range of hard engineering coastal defences is in place protecting the cliff base from marine erosion
  • the cliff still retreats as a result of rain entering the rock layers, increasing pore pressure and causing slumping
  • leaves clear scars and terraces on the cliff face and lobes of clay across the promenade
288
Q

Frost shattering/freeze thaw

How does it work?

A
  • mechanical
  • only found on coasts in a climate where the temperature changes daily above and below zero
  • water seeps into joints and cracks in the rock and when it freezes expands, entering pressure and forcing the rock apart
289
Q

Frost shattering/freeze thaw

What are the effects of it?

A

-angular rock fragments and a jagged cliff face are created, with scree slopes at the base

290
Q

Salt crystaliszation

How does it work?

A
  • mechanical
  • when waves break or splash cliffs on coastal rocks, the water evaporates, leaving behind sodium and magnesium salt compounds in joints and cracks in the rock
  • these salt crystals grow and exert pressure and force the rock apart
  • seawater may also enter porous rock and crystals grow inside the rock itself
291
Q

Salt crystaliszation

What are the effects of it?

A
  • angular rock fragments are loosened and fall to create scree slopes at the base of the cliff or rock faces crumble away
292
Q

Oxidation

How does it work?

A
  • chemical
  • Oxygen combines with iron-based minerals in a rock, causing a chemical breakdown of the minerals, as shown by red-orange rusty colour on a rock face
293
Q

Oxidation

What are the effects of it?

A
  • the rock minerals will no longer be bonded together and so the rock will crumble, making erosion easier
294
Q

Seaweed acids

How does it work?

A
  • biological
  • some seaweed cells (kelp) cells contain pockets of sulphuric acid, so when these cells break in contact with rock, the acid will dissolve some rock minerals
295
Q

Seaweed acids

What are the effects of it?

A

-rock minerals will no longer be bonded together and so parts of a rock will crumble, and these become points of greater erosion

296
Q

Boring molluscs

How does it work?

A
  • biological
  • many marine molluscs live on coastal rocks, scraping away at the rock surface to get food or boring a hole in the rock to make a home
  • example is the Piddock, which has a shell with serrated cutting edges
297
Q

Boring molluscs

What are the effects of it?

A
  • pebbles and rocks with holes bored into them are more easily moved around by the waves
  • the holes also provide weak points for other weathering processes to act
298
Q

mass movement types

A

mechanical
chemical
biological

299
Q

mass movement - mechanical processes

A
  • freeze thaw
  • salt crystaliszation
  • wetting and drying
300
Q

mass movement - mechanical processes

- freeze thaw explanation

A

Water gets into cracks, freezes and expands by up to 9%. This exerts pressure on the cracks which loosens and breaks apart rock. Most vulnerable are well jointed rocks. Only happens when daily temperatures fluctuate around zero degrees

301
Q

mass movement - mechanical processes

- freeze thaw effects

A

Creates angular rock fragments at the base of cliffs called scree and a jagged cliff face. Also can contribute to large rock falls.

302
Q

mass movement - mechanical processes

  • freeze thaw
  • vulnerable rocks
A
  • any rocks with cracks and fissures, especially high up cliffs away from salt spray
  • freezing is relatively uncommon on UK coasts, especially in south and salt spray can reduce its effect even further
303
Q

mass movement - mechanical processes

salt crystallisation

A
  • Salt spray or waves hitting cliffs make them wet with seawater.
  • This evaporates and leaves salt in cracks on the cliff. Over time, salt crystals form and grow, exerting pressure on the cracks and pores which loosens and breaks apart rock.
304
Q

mass movement - mechanical processes
salt crystallisation
effects

A

Creates angular rock fragments at the base of cliffs called scree. Some rock faces crumble away.

305
Q

mass movement - mechanical processes
salt crystallisation
-most vulnerable rocks

A

Most vulnerable are well jointed rocks (limestone) and porous rocks (Sandstone, chalk). Happens most in hotter climate.

306
Q

mass movement - mechanical processes
wetting and drying
explanation

A

Rocks rich in clay expand when they get wet and contract when they dry. This repeated process causes them to crack and break apart.

307
Q

mass movement - mechanical
wetting and dryingprocesses
effects

A

Cracks form in cliffs so they become vulnerable to slumping.

308
Q

mass movement - chemical processes

A
  • carbonation
  • oxidation
  • hydrolysis
309
Q

mass movement - chemical processes
-carbonation
explanation

A

Limestone slowly dissolves as it reacts with weak carbonic acid in rainwater.

310
Q

mass movement - chemical processes

  • carbonation
  • effects
A

Joints and cracks get wider on cliffs and wave cut platforms. This makes them more vulnerable to other weathering and mass movement processes.

311
Q

mass movement - chemical processes

  • carbonation
  • most vulnerable rocks
A

limestone and other carbonate rocks

312
Q

mass movement - chemical processes

  • hydrolysis
  • explanation
A

the breakdown of minerals to form new clay minerals, plus materials in solution, due to the effect of water and dissolved co2

313
Q

mass movement - chemical processes

  • hydrolysis
  • vulnerable rocks
A

igneous and metamorphic rocks containing feldspar and other silicate minerals

314
Q

mass movement - chemical processes

  • oxidation
  • explanation
A

-Oxygen combines with iron based minerals in a rock causing a chemical breakdown of the minerals shown by a red rusty colour on the rock face. Sandstones and shales often contain iron so are vulnerable.

315
Q

mass movement - chemical processes

  • oxidation
  • effect
A

Leads to crumbling of the cliff as sections are no longer bonded together.

316
Q

mass movement - chemical processes

  • oxidation
  • most vulnerable rocks
A

Sandstones, siltstones and shales often contain iron so are vulnerable as they can be oxidised

317
Q

mass movement - biological processes

A
  • plant roots
  • rock boring
  • seaweed acids
318
Q

mass movement - biological processes

  • plant roots
  • explanation
A

-Tree and plant roots growing into cracks can slowly widen them and cause them to break apart. Important process on vegetated rock faces.

319
Q

mass movement - biological processes

  • plant roots
  • effects
A

Can cause rock falls

320
Q

mass movement - biological processes

  • plant roots
  • most vulnerable rocks
A

an important process on vegetated cliff tops that can contribute to rockfalls

321
Q

mass movement - biological processes

  • rock boring
  • explanation
A

-Clams and molluscs bore (dig) into rock to make their homes. They can also secrete acids that dissolves rocks. Sedimentary rocks in the intertidal zone are vulnerable.

322
Q

mass movement - biological processes

  • rock boring
  • effects
A

Holes and weaknesses created are vulnerable to erosion and further weathering.

323
Q

mass movement - biological processes

  • rock boring
  • most vulnerable rocks
A

Sedimentary rocks in the intertidal zone are vulnerable.

324
Q

mass movement - biological processes

  • seaweed acid
  • explanation
A

Some seaweed species like kelp contain pockets of sulphuric acid that can burst on rocks and dissolve them.

325
Q

mass movement - biological processes

-effects

A

Leads to crumbling of the cliff as sections are no longer bonded together

326
Q

What are the different classifications of mass movement?

A

-Fall
-topple
-translational slide
rotational -slide/slumping
flow

327
Q

What are the different classifications of mass movement?

-fall

A
  • rockfalls or blockfalls, are a rapid form of mass movement
  • on coasts blocks of rock can be dislodged by mechanical weathering or by hydraulic action erosion
  • undercutting of cliffs by the creation of wave-cut notches can lead to large falls
328
Q

What are the different classifications of mass movement?

-topple

A
  • geological structure influences topples
  • where rock strata have a very steep seaward dip, undercutting by erosion will quickly lead to instability and blocks of material toppling seaward
329
Q

What are the different classifications of mass movement?

-translational slide

A
  • a very low angle seaward dip in strata will prevent falls

- material will tend to slide down the dip slope towards the sea

330
Q

What are the different classifications of mass movement?

-rotational slide/slumping

A
  • mass movements can occur along a curved failure surface
  • huge masses of material can slowly rotate downslope over periods lasting from days to years
  • water plays an important role in rotational slides
331
Q

What are the different classifications of mass movement?

-flow

A
  • flows are common in weak rocks such as clay or unconsolidated sands
  • these materials can become saturated, lose their cohesion and flow downslope
  • heavy rainfall combined with high tides can contribute to saturation

A Level Geography (20 decks)

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